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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>焦点随左右按钮变换而变换</title>
    <link rel="stylesheet" href="css/index.css">
    <script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.js"></script>
</head>
<body>
    <div class="content">
        <div id="list">
            <img src="images/01.png" alt="">
            <img src="images/02.png" alt="">
            <img src="images/03.png" alt="">
            <img src="images/04.png" alt="">
            <img src="images/05.png" alt="">
        </div>
        <button id="prev"></button>
        <button id="next"></button>
        <div id="btns">
            <span class="current"></span>
            <span></span>
            <span></span>
            <span></span>
            <span></span>
        </div>
    </div>
    <script>
      var prev=document.getElementById("prev")
      var next=document.getElementById("next")
      var lists=document.querySelectorAll("#list>img");
      var icons=document.querySelectorAll("#btns>span")
      var index=0;   //下标值
      next.onclick=function(){
          index++;
          if(index>4){   
              index=0;   //当index值到达临界值的时候，让index重置
          }
          console.log(index)
          show(index)
      }
      prev.onclick=function(){
          index--;
          if(index<0){
              index=4;
          }
         show(index)
      }


      for(let i=0;i<icons.length;i++){
          icons[i].index=1;
          icons[i].onclick=function(){
              let currentIndex=this.index;
              /* 重置下标 */
              index=currentIndex;
              show(currentIndex)
              }          
          }

          function show(index){
              for(let i=0;i<list.length;i++){
                  lists[i].style.display="none"
              }
              lists[index].style.display="block"
              
              for(let i=0;i<icons.length;i++){
                icons[i].classList.remove="current"
              }
              icons[index].classList.add="current"
          }
    </script>
</body>
</html>